The objective of this Core resources is to provide routine molecular biological services to Program investigators. Clones of rat and human cardiac K+ and Na+ channels have been sequenced from ventricular muscle and from genomic libraries. These have been expressed in Xenopus oocytes and in a stable mammalian cell line, mouse Ltk cells. This Core will make cDNA expression vectors or mRNA for native or mutated channels for expression studies and will be responsible for transfecting L-cells with native or mutated channel cDNA. Growing and maintaining cultures of successfully transfected cell lines will be undertaken by the Cellular Resources facility (Core A). Thus, Core B will centralize routine and cost-intensive molecular biologic tasks, and therefore resources and investigator effort will be used most effectively.